Manufacture of filaments or fibers of polyamides

ABSTRACT

1. A PROCESS FOR THE MANUFACTURE OF ANTISTATIC POL AMIDE FILAMENTS WHICH COMPRISES: FORMING A MOLTEN MIXTURE OF (A) A FILAMENT-FORMING SYNTHETIC LINEAR ALIPHATIC POLYAMIDE HAVING RECURRING AMIDE GROUPS IN THE BACKBONE AND HAVING A RELATIE VISOSITY IN THE RANGE OF 1.5 TO 2.9, MEASURED AS A 1% W./W TOGETHER WITH (B) FROM 2 TO 15% BY WEIGHT, BASED ON THE FILAMENTS OR FIBERS, OF AN ALKOXYLATED POLYAMIDE MANUFACTURED BY REACTION OF A OLYMIDE SELECTED FROM THE CONSISTING OF THE POLYCONDENSATES OF LACTAMS OF 4 TO 12 CARBON ATOMS AND POLYCONDENSATES OF THE SALTS OF DIAMINES CONDENSATES OF LACTAMS OF 4 TO 12 CARBON ATOMS AND DICARBOXYLIC ACIDS OF 4 TO 12 CARBONS ATOMS WITH A 1,2-ALKYLENE OXIDE IN A WEIGHT RATIO FO FROM 1:2 TO 1-5 AND TO PROVIDE A TOTAL MOLECULAR WEIGHT OF 10,000, COMPONENTS (A) AND (B) BEING SO THROUGHLY MIXED THAT SAID ALKOXYLATED POLYAMIDE IS PRESENT IN THE FINISHED FILAMENTS IN THE FORM OF PARTICLES HAVING A DIAMETER OF NOT MORE THAN 0.1; AND FINISHED FILAMENTS IN THE FORM OF PARTICLES HAVING A FILTER HAVING A PORE WIDTH OF NOT MORE THAN 20; AND SUBSEQUENTLY MELT SPINING SAID MIXTURE BEING MAINTAIND IN THIS MENTS, THE MOLTEN MIXTURE BEING MAINTAINED IN THIS PROCESS AT ELEVATE TEMPERATURES OF UP TO NOT MORE THAN 290*C. FOR A TOTAL PERIOD OF NOT MORE THAN 30 MINUT4S.

United States Patent US. Cl. 260857 TW 4 Claims ABSTRACT OF THEDISCLOSURE Manufacture of filaments or fibers of synthetic linearpolyamides containing from 2 to 15% by weight of alkoxylated polyamidesusing certain conditions concerning the fineness of subdivision,filtration and shaping.

This invention relates to a process for the manufacture of filaments orfibers containing alkoxylated polyamides.

It is well known that textiles and carpets of synthetic fibers includingpolyamides build up an electrostatic charge due to friction occurring inuse. Such electrostatic charges, in the case of textiles, may produce anunpleasant feel when said textiles are in contact with the human bodyor, in the case of carpets, persons walking thereon may receive highlyunpleasant shocks due to electrostatic discharges. These phenomena areparticularly observed when the relative humidity is low.

There has been no lack of attempts to obviate these undesirableproperties. For example, attempts have been made to increase the surfaceconductivity of polyamide filaments by applying antistatic agentsthereto, either together with the lubricant or in a subsequent step.Such agents are usually water-soluble, however, and consequently theireffectiveness disappears on washing. The effect may be made morepermanent by incorporating the agents in the polymer. This method isdescribed in US. Pat. 3,329,557, which teaches the incorporation ofpolyethylene glycols into polyamide filaments. However, the resultsobtained could still be improved upon, since the said polyethyleneglycols are extracted on repeated washing. These well-knowndisadvantages may, in theory, be overcome by subsequent cross-linkingwith, say, X-rays', but this solution is hardly economical.

It is an object of the invention to manufacture filaments or fiberswhich show a permanent greatly reduced tendency to antistatic build-upwithout the other properties of the fibers, such as their mechanical ortinctorial properties, being substantially impaired.

This object is achieved by a method of making filaments or fibers offilament-forming synthetic linear polyamides containing alkoxylatedpolyamides in an amount of from 2 to 15%, on the weight of the filamentsor fibers, Wherein a molten mixture of the filament-forming syntheticlinear polyamides and alkoxylated polyamides is subjected to thoroughmixing so that the alkoxylated polyamides are present in the finishedfilaments in the form; of particles having a diameter of not more than0.1,u., and the molten mixture is filtered at least once through afilter having a pore width of not more than 2071, the mixture isconverted to chip form if desired, and the mixture is melt spun, themolten mixture being maintained at temperatures of up to not more than290 C. for a total period of not more than 30 minutes.

By filament-forming synthetic linear polyamides of high molecular weightwe mean those having recurring amide groups in the backbone.

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Suitable filament-forming or fiber-forming synthetic linear polyamidesare, for example, the polycondensates of lactams having from 4 to 12carbon atoms, such as e-caprolactam, octolactam, dodecanolactam ormixtures of said lactams, and the polycondensates of salts of diaminesand dicarboxylic acids having from 4 to 12 carbon atoms, such as thesalts of adipic acid, suberic acid or sebacic acid, and hexamethylenediamine, octamethylene diamine or dodecamethylene diamine or mixedcondensates of said polyamide-forming materials. Particularly suitableare polycaprolactam; and polyhexamethylene adipamide. Thefilament-forming or fiber-forming polyamides may contain an excess ofBasic groups or they may have a content of sulfo groups or alkali metalsulfonate groups. Conveniently, the polyamides to be modified ha'verelative viscosities in the range 1.5 to 2.9.

Polyamides alkoxylated with 1,2-alkylene oxides may be manufactured byknown processes, for example by the method described in Belgian Pat.665,018 comprising the reaction of 1,2-alkylene oxides, for exampleethylene oxide and/ or 1,2-propylene oxide, with polyamides underpressure and at elevated temperatures, in particular at temperaturesranging from 60 to C. The reaction may be carried out in the presence orabsence of organic solvents and/or reducing or oxidizing agents, thealkylene oxides being reacted with the polyamides preferably in a ratioof from 2 to 5:1 by weight. It has been found advantageous to usealkoxylated polyamides having a total molecular weight of at least10,000 and in particular from 20,000 to 80,000.

Suitable polyamides from which the alkoxylated polyamide antistaticagents may be manufactured are for example conventionally producedpolycondensates of lactams having from 4 to 12 carbon atoms, such ase-caprolactam, octolactam, dodecanolactam or mixtures of said lactams,the polycondensates of salts of diamines and dicarboxylic acids havingfrom 4 to 12 carbon atoms, such as the salts of adipic acid, subericacid or sebacic acid, and hexamethylene diamine, octamethylene diamineor dodecamethylene diamine or copolyamides of said polyamide-formingmaterials. Particularly suitable are all those polyamides which have lowcrystallinity, for example copolyamides or polyamides which have beenprepared by quenching the polymer melt, for example moltenpolycaprolactam.

The amount of alkoxylated polyamides used is conveniently from 2 to 15%and in particular from 4 to 10% w./w. of the weight of the filaments orfibers. It is possible to use larger proportions, but this leads tochanges in the properties of the filaments or fibers.

The solid components, i.e. the filament-forming polyamides and thealkoxylated polyamides, may be melted separately or together. Thecomponents may be mixed in a conventional single-worm or twin-wormextruder, of which one or both of the worms may be axially displaceableif desired. Static mixers having stationary conducting elements may alsobe used to advantage. Adequate mixing is usually obtained using staticmixers having 15 or more elements. Static mixers of this kind aredescribed for example in US. Pats. 3,286,992 and 3,404,689 and GermanPublished Application 1,178,404. Conditions should be such as to achievesuch thorough mixing that the alkoxylated polyamides, which form aseparate phase in the filaments after cooling and drawing, have aparticle diameter of not more than 0.1 4. The degree of mixing requiredto achieve this end may be previously found by simple experiment. Thelength of the separate particles of alkoxylated polyamides in thefilaments after drawing is generally a multiple of their diameter, forexample about 111 or more. It is an important feature of the process ofthe invention that filtration of the molten mixture of components iscarried out at least once through filters having pore widths or not morethan 201L- Examples of suitable filters are metal sieves or, inparticular, sintered metal filters such as sintered metal plates orsintered metal tubelets.

Following the thorough mixing and filtration, the molten mixture may, ifdesired, be converted to chips and subsequently melt-spun to filamentsor fibers. Alternatively, the molten mixture may be thoroughly mixed andfiltered and immediately melt-spun to filaments or fibers withoutintermediate conversion to chip form. Another alternative is to carryout mixing and filtration in the spinning apparatus by using a spinningextruder capable of providing thorough mixing and placing a filterhaving a pore width of less than 20g immediately downstream of thespinning nozzle, which filter is advantageously an appropriate sinteredmetal filter.

It is important that the molten mixture of filamentforming polyamide andalkoxylated polyamide is maintained at temperatures of not more than 290C. and generally at from 250 to 290 C. for a total period of not morethan 30 minutes including the melt-spinning time. The time during whichthe mixture may be in chip form in a colder state is, of course, notincluded.

The filaments are made using conventional spinning systems wherein, ofcourse, the conditions usually observed in the manufacture of polyamidefilaments, such as the exclusion of oxygen and the use of certain lowmoisture contents, must be met. The filaments or fibers produced bymelt-spinning may have a round crosssection or a profiled cross-sectionsuch as a trilobate or tetralobate cross-section. The filaments may bein the form of two-component filaments with other filamentformingmaterials. Conveniently, the filaments or fibers of the invention arestretched, for example at a draw ratio of from 1:2.5 to 1:4.5. Thefilaments or fibers may also be texturized, for example by thefalse-twist or stutter-box method or by texturizing in moving gas media.

The filaments or fibers may incorporate conventional additives such aspigments, for example titanium dioxide, or light stabilizers, heatstabilizers, and stabilizers to prevent the degradation of polyetherchains.

The filaments or fibers produced by the method of the invention aredistinguished by their greatly reduced tendency to build upelectrostatic charges. This good antistatic behavior remains afterrepeated washing.

Electrostatic build-up on textile articles may be determined by themethod proposed by Heyl & Liittgens (Kunststoife, Vol. 56, 1966, p. 51).A suitable method as regards carpets is the stroll test (Test Method forDetermining the Static Propensity of Carpets, Report American CarpetInstitute, Aug. 19, 1968).

It is a great advantage that the good antistatic properties of thefilaments or fibers produced by the method of the invention are notobtained at the expense of the mechanical and tinctorial properties ofthe filaments or fibers. The process of the invention is distinguishedin that the yields produced in spinning and drawing are high as comparedwith unmodified polyamides, which means that the number of defects foundin the subsequent stages of warping and knitting is low. The sameapplies to the use of the filaments in the manufacture of carpets, wheregreat advantage are found, for example, in the steps of texturizing andtufting. The quality of the filaments is tested by the conventionaltechnological tests on mechanical properties and dyeability. The valuesfound for the filaments produced by the invention hardly differ fromthose provided by the corresponding unmodified polyamides. Indeed, thefilaments modified by the present invention can usually by dyed deeperand more level shades a frequently desirable feature. Since thestreak-free dyeing of conventional polyamides remains a problem, theabove improvement as concerns dyeability is particularly advantageous.

The filaments made in accordance with the present invention may be wovenor knitted to textile articles such as underwear and shirts withadvantageous results. The quality required in such articles isparticularly high and the measures of the invention are thereforeespecially efiective for this application. Filaments made in the mannerproposed by the present invention may also be used successfully incarpets, both in the form of continuous filaments and as staple fibers.A distinct improvement in the quality of the filaments is achieved ascompared with prior art modifying processes for the manufacture oftwophase antistatic fibers.

In the following Example the parts and percentages are by weight. Therelative viscosities (1 are measured on a 1% w./w. solution in 98% H at20 C.

EXAMPLE A Werner & Pfieiderer twin-worm extruder ZSK 53 is fed with 92.5parts of extracted and dried polycaprolactam chips having a relativeviscosity (1 of 2.4 and delustered with 1.6% of TiO and simultaneouslywith 7.5 parts of an ethoxylated polycaprolactam showing a ratio ofpolycaprolactam to ethylene oxide of 1:3.6 by weight. Heating iseffected so that the temperature of the molten mixture rises from 220 C.at the feed end to from 266 to 268 C. at the output end of the extruder.At a speed of rpm. the throughput is 80 kg./hr. The residence time ofthe melt in the extruder is about 2 minutes. t

At the end of the screws there is provided a filter unit which is heatedat 25 0 C. and is fitted with metal sieves of 17 mesh. The filteredmolten mixture is extruded in four strands which are cooled in a waterbath and then granulated. The granules are dried to a water content ofless than 0.1% and then melt-spun to filaments 144 f 10 dtex. using anextruder provided with a sintered metal filter having an average porewidth of about 18 The residence time of the molten mixture in thespinning system is about 15 minutes. The resulting filaments are thenstretched at a draw ratio of 113.28 to form filaments 44 f 10 dtex. Thedrawing yield is 96% based on cops weighing 1 kg.

Table 1 below gives the results of tests in comparison with unmodifiedpolycaprolactam filaments:

This table shows that there are no substantial differences between thetwo types of filament.

The ethoxylated polycaprolactam is present in the filaments as aseparate phase in the form of very small rods having a diameter of notmore than 0.1 4. Using the apparatus described by Heyl & Liittgens (10c.cit.) for measuring the electrostatic build-up, knitted material madefrom the filaments of the invention and which has been washed five timeshas a field strength of only 60 volts/ cm. when measured at 50% relativehumidity after being rubbed for 4 minutes against a knitted fabric ofunmodified polycaprolactam. Unmodified polycaprolactam in the form ofknitted fabric which has been washed five times shows a field ofstrength of 2,400 volts/cm. when measured under similar conditions.

Knitted fabric made from the filaments of the invention shows veryuniform affinity for acid dyes as well as disperse dyes and also shows adistinctly higher color yield than unmodified polycaprolactam material.

We claim: 1. A process for the manufacture of antistatic polyamidefilaments which comprises: forming a molten mixture of (a) a.filament-forming synthetic linear aliphatic polyamide having recurringamide groups in the backbone and having a relative viscosity in therange of 1.5 to 2.9, measured as a 1% w./w. solution in 98% H 80 at 20C.,

together with (b) from 2 to 15% by weight, based on the filaments orfibers, of an alkoxylated polyamide manufactured by reaction of apolyamide selected from the group consisting of the polycondensates oflactams of 4 to 12 carbon atoms and polycondensates of the salts ofdiamines and dicarboxylic acids of 4 to 12 carbon atoms with a1,2-alkylene oxide in a weight ratio of from 1:2 to 1:5 and to provide atotal molecular weight of 10,000 to 80,000,

components (a) and (b) being so thoroughly mixed that said alkoxylatedpolyamide is present in the finished filaments in the form of particleshaving a diameter of not more than 0.1 1.; and

filtering said molten mixture at least once through a filter having apore width of not more than 20 and subsequently melt spinning saidmixture into solid filaments, the molten mixture being maintained inthis process at elevated temperatures of up to not more than 290 C. fora total period of not more than 30 minutes.

2. A process as claimed in Claim 1, wherein the filament-forming linearpolyamide (a) is thoroughly mixed with from 4 to 10% by weight ofalkoxylated polyamide (b). a

3. A process as claimed in Claim 1 wherein the mixture is converted intochip form or granulated intermediate the filtering step and the meltspinning step.

4. The filamentary product obtained by the process of Claim 1.

References Cited UNITED STATES PATENTS 3,099,067 7 1963 Merriam et al264-210 F 3,329,557 7/1967 Mag-at et a1. 161--172 3,577,308 5/1971Drunen et a1. 264-171 3,632,666 1/1972 Okazaki et al 260857 PE 3,639,5022/1972 Okazaki et a1. 260857 PE 3,707,341 12/ 1972 Fontiju et a1 264176F 3,725,503 4/1973 Kunde et al 260-857 PG JAY H. WOO, Primary ExaminerUS. Cl. X.R.

260-78 SC; 264-176 F

1. A PROCESS FOR THE MANUFACTURE OF ANTISTATIC POL AMIDE FILAMENTS WHICHCOMPRISES: FORMING A MOLTEN MIXTURE OF (A) A FILAMENT-FORMING SYNTHETICLINEAR ALIPHATIC POLYAMIDE HAVING RECURRING AMIDE GROUPS IN THE BACKBONEAND HAVING A RELATIE VISOSITY IN THE RANGE OF 1.5 TO 2.9, MEASURED AS A1% W./W TOGETHER WITH (B) FROM 2 TO 15% BY WEIGHT, BASED ON THEFILAMENTS OR FIBERS, OF AN ALKOXYLATED POLYAMIDE MANUFACTURED BYREACTION OF A OLYMIDE SELECTED FROM THE CONSISTING OF THEPOLYCONDENSATES OF LACTAMS OF 4 TO 12 CARBON ATOMS AND POLYCONDENSATESOF THE SALTS OF DIAMINES CONDENSATES OF LACTAMS OF 4 TO 12 CARBON ATOMSAND DICARBOXYLIC ACIDS OF 4 TO 12 CARBONS ATOMS WITH A 1,2-ALKYLENEOXIDE IN A WEIGHT RATIO FO FROM 1:2 TO 1-5 AND TO PROVIDE A TOTALMOLECULAR WEIGHT OF 10,000, COMPONENTS (A) AND (B) BEING SO THROUGHLYMIXED THAT SAID ALKOXYLATED POLYAMIDE IS PRESENT IN THE FINISHEDFILAMENTS IN THE FORM OF PARTICLES HAVING A DIAMETER OF NOT MORE THAN0.1; AND FINISHED FILAMENTS IN THE FORM OF PARTICLES HAVING A FILTERHAVING A PORE WIDTH OF NOT MORE THAN 20; AND SUBSEQUENTLY MELT SPININGSAID MIXTURE BEING MAINTAIND IN THIS MENTS, THE MOLTEN MIXTURE BEINGMAINTAINED IN THIS PROCESS AT ELEVATE TEMPERATURES OF UP TO NOT MORETHAN 290*C. FOR A TOTAL PERIOD OF NOT MORE THAN 30 MINUT4S.